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250sx NECJ Jetting

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I switched to 42 pilot, NECJ needle (3) and a 172 main, and I am at 500' at around 90 degrees. Bike feels INCREDIBLE until I get past 3/4 throttle onto the main jet. When I WOT it seems to just rev but not really go anywhere. Is my main too rich?

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2013 250xc-w
38 Pilot
N8RJ (3)
165 Main.
Turbine core 2 and FMF Fatty
Bike runs strong from 500' up to 5000+
I'd say your main is a little large.

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Sounds too large to me. But you can check it really easily. This technique is from Mikuni but I think it works on all carbs.

 

ROLL-OFF:

The Roll-Off technique is the quickest and is almost as accurate as the Roll-On method. First, one gets the engine warm on the way to a safe roadway. If there is room, use fourth gear as this allows more time to assess the result.

Now, get the engine rpm high enough that it is on the cam and in its power band. This may need to be as high as 4000 rpm with some cam choices. Apply full throttle. Let the engine accelerate for a couple of seconds until it has settled in and is pulling hard. Quickly roll the throttle off to about the 7/8ths position. When you do this, the mixture richens slightly for a second or so.
If the engine gains power as you roll the throttle off, then the main jet is too small and you need to fit a larger one. 
If the engine staggers slightly or has a hard hesitation, then the main jet is too large and you need to fit a smaller one.

Edited by LSHD

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4 hours ago, 1999yz125 said:

I switched to 42 pilot, NECJ needle (3) and a 172 main, and I am at 500' at around 90 degrees. Bike feels INCREDIBLE until I get past 3/4 throttle onto the main jet. When I WOT it seems to just rev but not really go anywhere. Is my main too rich?

all factory 2 strokes seem to be at lest 2 sizes to big on the main and you usually drop 2-3 sizes with the suzuki needle ( thin tipped) so 162-165 should be good

 

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Alright thanks guys, I'm going to throw a 165 in there and try the roll-off technique LSHD mentioned. 

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